This invention relates to chip semiconductor light-emitting devices and, more particularly, to a chip semiconductor light-emitting device for emitting color mixture of light by the use of light-emitting diode (LED) elements different in emission-light color.
Conventionally, there has been known a chip light-emitting device having a light source arranged with LED elements different in emission-light color to emit color mixture of light. FIG. 7 and FIG. 8 depict an example of such a device, wherein FIG. 7 shows a perspective view of a chip light-emitting device 10 while FIG. 8 is a side view of FIG. 7 as viewed in a section on line Axe2x80x94A. In FIG. 7, the chip light-emitting device 10 has a baseboard 2 on which electrodes 3a, 3b and electrodes 4a, 4b are formed of conductive material.
In one end of the baseboard 2, semi-circular cutouts 8a, 8a are provided to form, thereon, conductive films, such as electroplated layers, respectively connected to the electrodes 3b and 4b. Also, in the other end of the baseboard 2, semi-circular cutouts are similarly provided. The conductive films, such as electroplated layers, formed on the semi-circular cutouts extend down to a backside of the baseboard.
An LED element 1a is mounted by die bonding on the electrode 3a, and an LED element 1b is mounted by die bonding on the electrode 4a. The LED element 1a emits, e.g. red light. The LED element 1b emits light of different color from the light color by the LED element 1a, e.g. green light. The LED element 1a is electrically connected to the electrode 3b through wire bonding using a metal wire 5a. The LED element 1a is electrically connected to the electrode 4b through wire bonding using a metal wire 5b. 
The baseboard 2 mounting thereon the LED elements 1a, 1b is rested with a reflector 6 formed of opaque resin. Light-transmissive resin 7 such as epoxy resin is filled in an aperture defined in the reflector 6 as shown in FIG. 8, thereby forming a chip light-emitting device 10. The reflector 6 is oval as viewed in plan and has a slant surface 6a having upward inclination with respect to a contact surface with the baseboard 2. The reflector 6 is formed by injection-molding, e.g. of white-colored liquid-crystal polymer.
The chip light-emitting device 10 is surface-mounted on a printed circuit board. Electrical connection is made between the conductive films formed on the backside of the baseboard 2 through the semi-circular cutouts and the circuit pattern on the printed circuit board. By operating the LED element 1a for red-light emission and the LED element 1b for green-light emission, the chip light-emitting device 10 emits light mixed with red and green.
The operation of the chip light-emitting device 10 will be explained with reference to FIG. 8. It is now assumed that the LED element 1a has a light source Sa. The output light of the light source Sa reflects upon a slant surface 6a of the reflector 6 at a lower side than a belly thereof and turns into reflection light Ra directed toward a luminous center P of the chip light-emitting device 10. Also, the output light from the light source Sb of the LED element 1b reflects upon a slant surface 6a of the reflector 6 as a surface closer to the baseboard and turns into reflection light Rx directed toward the luminous center P of the chip light-emitting device 10.
In this manner, the chip light-emitting device 10 has the reflector 6 formed with a vertically-penetrating slant surface 6a to reflect and radiate the output light of the LED element by the reflector. The reflection light is collected to a luminous center P, thereby improving luminous efficiency.
Also, the output light from the light source Sa of the LED element 1a and the output light from the light source Sb of the LED element 1b, in the vicinity of a top end of the slant surface 6a of the reflector 6, respectively turn into reflection light Rb and Ry to be emitted from the chip light-emitting device 10.
FIG. 9 is an explanatory view showing, in a vertical sectional view of FIG. 8, a luminous-intensity distribution given by the LED elements 1a, 1b. In FIG. 9, Ia is a luminous-intensity distribution of reflection light given by the LED element 1a while 1b is a luminous-intensity distribution of reflection light given by the LED element 1b. On a right side of the luminous center P, the LED element 1a arranged distant from the slant surface 6a provides reflection light upon nearly an upper half of the slant surface 6a.
Meanwhile, on a left side of the luminous center P, the LED element 1b arranged distant from the slant surface 6a provides reflection light nearly upon an upper half of the slant surface 6a. In this manner, the luminous-intensity distributions by the LED elements 1a, 1b are different in characteristic on between the left and right sides of the luminous center P.
As shown in FIG. 9, in the conventional chip light-emitting device, the reflector slant surface is set with a constant inclination angle xcex8x. Consequently, the luminous-intensity distribution is different on left and right sides with respect to the luminous center P between the LED element arranged closer to the slant surface and the LED element arranged closer to the slant surface. Due to this, there is emphasis on any of light colors emitted by-the LED elements 1a and 1b depending upon a position viewing the light emission surface of the chip light-emitting device. Thus, there has been a problem that there is difference in color-mixture tone and hence difference in color of emission light from the chip light-emitting device.
As for the LED element arranged distant as viewed from the slant surface, the output light reflects almost on an upper half only of the slant surface. Thus, there has been a problem that there is decrease in amount of light directed toward a luminous center and hence decrease in a center luminous intensity of the chip light-emitting device 10.
Therefore, it is a primary object of this invention to provide a novel chip semiconductor light-emitting device.
Another object of the invention to provide a chip light-emitting device capable of making even the degree of mixing colors.
A chip semiconductor light-emitting device according to the present invention comprises: a baseboard; first and second conductors formed on the baseboard; first and second semiconductor light-emitting elements respectively mounted on the first and second conductors and different in color of emission light; and a reflector placed on the baseboard such that a slant surface thereof surrounds the first and second semiconductor light-emitting elements; the slant surface including first and second reflection surfaces continuing in a thickness direction of the reflector and respectively having first and second inclination angles, the first reflection surface being closer to the baseboard and the second reflection surface more distant from the baseboard; the first and second angles being set such that first output light of the first semiconductor light-emitting element arranged closer to the first reflection surface provides a first angle, given between reflection light reflected on a lower side of the first reflection surface and reflection light reflected on an upper side of the first reflection surface, equal to a second angle, given between reflection light reflected on a lower side of the second reflection surface and reflection light reflected on an upper side of the second reflection surface that are provided by second output light of the second semiconductor light-emitting device arranged distant from the first reflection surface.
In an embodiment, the first angle is represented by xcex8p and the second angle by xcex8q. The first inclination angle xcex8a and xcex8b are set to have a relationship xcex8p=xcex8q. This makes equal the directivity of reflection light due to the first output light of the first semiconductor light-emitting element to the directivity of reflection light due to the second output light of the second semiconductor light-emitting element, and hence, on the light-emitting surface, a luminous-intensity distribution due to the first semiconductor light-emitting element to a luminous-intensity distribution due to the second semiconductor light-emitting element. Accordingly, the first output light and the second output light are mixed of color homogeneously.
Furthermore, if the first reflection surface and the second reflection surface are continued almost in a center of the reflector with respect to the thickness direction, the first and second reflection surfaces reflect efficiently the first output light and the second output light. This maximizes the amount of each of reflection light travelling toward a luminous center. Due to this, center luminous intensity can be increased for the chip semiconductor light-emitting device.
Meanwhile, by extending the opposite ends of the reflector to the cutouts formed in the baseboard opposite ends, the reflector can be size-increased. This can further increase the center luminous intensity of the chip light-emitting device.
Incidentally, the reflector aperture in plan shape can be selected to the purpose from among arbitrary forms including a circular form in addition to the oval and rectangular forms as were described in the embodiments.